The two-spotted spider mite (Tetranychus urticae) is the most common of all plant pest mites and has been reported on more than 200 plant species. They are mites and not insects.
Not only do insecticidal soaps work on pesky insects, they also kill spider mites.
Photo Credit: ©2003 Buglady Consulting
What does a two-spotted spider mite look like?
This pest is easy to identify because its name gives it away: It has two spots on its back. These spots can be seen with a hand lens and vary in color from green to red to purple.
The life cycle of the two-spotted spider mite depends on temperature: In warm weather, this mite can complete its life cycle in as little as five days. Adult females can live two to four weeks and can lay several hundred eggs during that time. Populations especially thrive in hot, dry weather, so under these conditions, watch them close – they can creep up on you. Two-spotted spider mites overwinter as adults in leaf litter and under bark, not as eggs. So when it warms up in spring, they crawl out, ready to mate.
What kind of damage do two-spotted spider mites do?
Plant damage from two-spotted spider mites is easy to see. Leaves can have bronzing on the foliage or a flecked look to them. When numbers are high, fine webbing can be seen on the plants, as well as cast skins that look like white flakes. As mites grow they shed their skins, just like snakes do.
How do you control two-spotted spider mites?
Insecticidal soaps and oils offer great control for this mite and its eggs, but always read the product label and make sure your application is listed. This is to prevent you from damaging you plant. Special care must also be given to get good spray coverage with these products. Oils and soaps don’t have systemic properties, which means they must come in contact with the mites to get the kill. If the soap or oil is just sprayed on the tops of leaves, you won’t get contact on the lower side of the leaves, where two-spotted spider mites are likely to be. A word of warning, though: You can burn leaves with horticultural oils. These products need to be applied when it’s cool out. Make sure your plants were watered well the day before you apply your control – never spray wilted plants. Following labeled rates also reduces the risk of leaf damage. Always follow label directions!
If biological control is your preferred control method, there are several predators out there that fight against two-spotted spider mites, feeding on the adults and eggs. Phytoseiulus persimilis is the most poplar beneficial for this pest. You can purchase predatory mites (Phytoseiulus persimilis and Amblyseius [Neoseiulus] californicus), minute pirate bugs (Orius insidiosus) and predatory beetle (Stethorus) from commercial insectaries. (You can order through the Internet.) You can also invite many of these beneficial insects to your garden by selecting plants that attract them, such as dill, calendula and yarrow, among others.
Spider mites can be a very common problem, but once you learn to recognize the symptoms, you can treat and stop this problem before it spreads.